Tor can be thought of like a secure proxy.
I experimented with it during my research on Replacing Firefox.
UPDATE: Tor has been subverted for some time.
I know when and how, with confirmation, but not by whom.
It must not be used for high-level security requirements (governmental, military, international) and probably even mid-level requirements (corporate, police). Little people using it as a proxy are fine.
Don't do anything illegal with it if you're within three degrees of a Bad Guy. So.. don't use it for anything illegal. Remember that PRISM records everything, so that, once flagged, you can be found retroactively guilty (even by association) for past internet usage.
Tor Browser ∞
Tor Browser is:
- An audited, and patched version. The Tor developers cannot keep up with Mozilla's rapid release schedule.
Tor Browser is pretty cool, but this makes yet another browser instance, yet more preferences to be tweaked.
Preferences cannot simply be copied over from an existing profile, because who knows what poor security choices may have been made with it. Tweaking them all by hand would be a nightmare.
Firefox had, perhaps has and certainly will have in the future, bugs. Some are security bugs. Introducing subtle bugs into Firefox is a simple way for Bad people to diminish the security of the Tor Browser.
One of the problems with security is that we make certain assumptions. Unless we're open minded and do a lot of research, we have an unjustified feeling of security often in cases when we're not even close to safe.
There were some things which surprised me to learn or be reminded of.
Funnelling everything through a proxy isn't as good a solution as one would think.
- Not all applications respect proxy settings.
Mixed SSL and non-SSL content ∞
It's possible for a Tor exit server or the final destination server to inject arbitrary code or otherwise have security leaks in a page one might view.
Some browsers notify the user when non-secure content is found within a secure page. The user can then choose to not continue loading the page.
Some browsers have a feature over and above that, where they discard the non-secure content and still continue to display the secure content.
2 preferences have been added to block loading contents from non-SSL (http) sites on SSL (https) pages. Scripts, stylesheets, plug-in contents, inline frames, Web fonts and WebSockets can be blocked with
security.mixed_content.block_active_content, and other static contents like images, audios and videos can be blocked with
This preference will finally be enabled by default in Firefox 23.
However, as of 2013-06-19, the Tor browser uses a patched Firefox 17.0.6 so this functionality is completely absent. One can entire view both secure and non-secure content, or view nothing at all.
More thorough solutions ∞
Tails is a live boot environment that includes Tor Browser.